The LYIT are through to the CUFL Division 1 League final after beating TUS Midwest at the AUL Complex in Dublin with the help of a hat-trick from Pat Loughrey.
The Letterkenny side had to come from behind to force extra time and seal their place in the decider.
Having been 2-0 nil at half time they pulled it back to 2-2 before adding two further goals to win 4-2.
The other goal was scored by Joel Bradley Walsh.
The LYIT will play the winners of MTU Cork or Dundalk IT in the final.